The present invention relates to an electrostatic chuck and a method of fabricating the same.
An electrostatic chuck is used to electrostatically hold a substrate during processing, for example, to hold a silicon wafer in a chamber during semiconductor processing. The electrostatic chuck typically comprises an electrode covered by a dielectric, the electrode being electrically chargeable to form or sustain a plasma in the chamber. The plasma is an electrically conductive gaseous medium that may be formed by coupling electromagnetic energy, such as RF energy, into the chamber. For example, the plasma may be generated by inductive or capacitive coupling of energy to the gas. The electrode may also be charged by a voltage to generate an attractive electrostatic force that holds the substrate to the chuck. A heat transfer gas, such as helium, may also be provided to the backside of the substrate via holes that extend through the electrostatic chuck.
One problem with conventional electrostatic chucks arises during their use in plasma processes, especially high density plasma processes. The plasma can permeate into, or may form in, gaps and apertures in the electrostatic chuck. For example, the potential applied to the electrode may cause formation of glow discharges or electrical arcing in or about the helium gas holes passing through the electrostatic chuck. This is especially a problem when the gas holes extend through an electrode of the electrostatic chuck that is powered with a RF voltage, for example, to ignite or sustain the plasma in the chamber. The RF voltage may permeate to couple to the gas traveling through the gas holes to generate a plasma therein.
It is known to provide a dielectric insert in the gas hole to reduce plasma formation therein. The dielectric insert allows the passage of gas therethrough while reducing or preventing plasma formation therein. However, conventional methods of manufacturing the electrostatic chuck with the dielectric insert may sometimes result in cracking or fracturing about the portion of the electrostatic chuck surrounding the dielectric insert. Also, it is difficult to insert the dielectric insert into the gas hole of the electrostatic chuck without damaging the gas hole or the surrounding regions. This is especially a problem in the manufacture of electrostatic chucks made from ceramic materials which may be brittle and thereby undergo brittle fracture.
Thus, it is desirable to have an electrostatic chuck capable of reducing plasma formation about or in the electrostatic chuck, for example, in gas holes extending through the electrostatic chuck. It is also desirable to have a method of manufacturing the electrostatic chuck that allows for the robust production of electrostatic chucks. It is further desirable to allow for the efficient production of ceramic electrostatic chucks.
The present invention satisfies these needs. A method of fabricating an electrostatic chuck capable of holding a substrate in a chamber is provided. The method comprises forming an at least partially sintered a dielectric insert, forming a dielectric preform comprising an electrode and a gas conduit, and placing the dielectric insert in the gas conduit of the dielectric preform, and sintering the dielectric preform and the dielectric insert.